Thermoplastic adhesives, otherwise known as “hot melt” adhesives have been widely used in industry for adhering many types of products. Hot melt adhesive dispensing systems generally include a dispenser coupled with one or more dispensing guns, heated hoses fluidly connected to the guns, and a dispensing unit for melting and supplying heated liquid adhesive to the guns through the heated hoses. The dispensing units of conventional hot melt adhesive systems include a tank, a heater, a pump, a pump manifold, and a controller. The heater is generally located in a base of the tank for melting and heating adhesive material received into the tank in solid or semi-solid form. The pump manifold has an inlet connected to the tank and has multiple outlet ports adapted for connection to the heated hoses.
After the adhesive material is melted and heated in the tank, a pump operatively coupled to the tank and the pump manifold pumps liquid adhesive from the tank, through the pump manifold and heated hoses to the dispensing guns. Typically, the guns are connected to their own manifold. The controller controls the power supplied to the tank heater and heated hoses to maintain the liquid adhesive at an appropriate viscosity and temperature, depending on the application. The controller is also used to control many other operations of the system.
In conventional dispensing unit designs, a filter is provided to capture particulate material which may be entrained in the liquid adhesive prior to supplying the adhesive to the dispensing gun manifold(s). Primarily, the filter prevents clogging of the system downstream, such as at the dispensing guns. The filter is generally located in the pump manifold so that it may be easily accessed for servicing or replacement. In some dispensing unit configurations access to the pump manifold is difficult, due to the position of the pump manifold or interference with hoses or other components, and it is therefore desired to locate the filter in a more convenient location while retaining the filter within the flow path of the liquid adhesive.
A need therefore exists for a dispensing unit of a hot melt adhesive dispensing system having a filter which is conveniently located for easy access and which can be utilized in arrangements where the manifold is difficult to access.